Absorption mechanism of dopamine/DOPAC modified TiO 2 nanoparticles by time-dependent density functional theory calculations

Abstract

Donor-modified TiO 2 nanoparticles are interesting hybrid systems shifting the absorption edge of this semiconductor from the ultra-violet to the visible or infrared light spectrum, which is a benefit for several applications ranging from photochemistry, photocatalysis, photovoltaics, or photodynamic therapy. Here, we investigate the absorption properties of two catechol-like molecules, i.e. dopamine and DOPAC ligands, when anchored to a spherical anatase TiO 2 nanoparticle of realistic size (2.2 nm), by means of time-dependent density functional theory calculations. By the differential absorbance spectra with the bare nanoparticle, we show how it is possible to determine the injection mechanism. Since new low-energy absorption peaks are observed, we infer a direct charge transfer injection, which, unexpectedly, does not involve the lowest energy conduction band states. We also find that the more perpendicular the molecular benzene ring is to the surface, the more intense is the absorption, which suggests aiming at high molecular packing in the synthesis. Through a comparative investigation with a flat TiO 2 surface model, we unravel both the curvature and coverage effects.

References in corpus (7)

• Octopus, a computational framework for exploring light-driven phenomena and quantum dynamics in extended and finite systems
• A real-space, rela-time method for the dielectric function
• Self-Energy and Excitonic Effects in the Electronic and Optical Properties of TiO2 Crystalline Phases
• Quasiparticle and Optical Properties of Rutile and Anatase TiO${}_2$
• Modified optical absorption of molecules on metallic nanoparticles at sub-monolayer coverage
• Modelling Realistic TiO2 Nanospheres: a Benchmark Study of SCC-DFTB against Hybrid DFT
• Photoexcited Carriers Recombination And Trapping In Spherical Vs Faceted TiO2 Nanoparticles